In George Orwell’s “1984,” government censors erase all traces of news articles embarrassing to Big Brother by sending them down an incineration chute called the “memory hole.” On Friday, it was “1984” and another Orwell book, “Animal Farm,” that were dropped down the memory hole — by Amazon.com. In a move that angered customers and generated waves of online pique, Amazon remotely deleted some digital editions of the books from the Kindle devices of readers who had bought them. An Amazon spokesman, Drew Herdener, said in an e-mail message that the books were added to the Kindle store by a...